Nominal Model-Based Sliding Mode Control with Backstepping for 3-Axis Flight Table

Based on nominal model, a novel global sliding mode controller （GSMC） with a new control scheme is proposed for a practical uncertain servo system. This control scheme consists of two combined controllers, One is the global sliding mode controller for practical plant, the other is the integral backstepping controller for nominal model. Modeling error between practical plant and nominal model is used to design GSMC. The steady-state control accuracy can be guaranteed by the integral backstepping control law, and the global robustness can be obtained by GSMC. The stability of the proposed controller is proved according to the Lyapunov approach. The simulation results both of sine signal and step signal tracking for 3-axis flight table are investigated to show good position tracking performance and high robustness with respect to large and parameter changes over all the response time.

Study on soil-pile-structure-TMD interaction system by shaking table model test

The success of the tuned mass damper (TMD) in reducing wind-induced structural vibrations has been well established. However, from most of the recent numerical studies, it appears that for a structure situated on very soft soil, soil-structure interaction (SSI) could render a damper on the structure totally ineffective. In order to experimentally verify the SSI effect on the seismic performance of TMD, a series of shaking table model tests have been conducted and the results are presented in this paper. It has been shown that the TMD is not as effective in controlling the seismic responses of structures built on soft soil sites due to the SSI effect. Some test results also show that a TMD device might have a negative impact if the SSI effect is neglected and the structure is built on a soft soil site. For structures constructed on a soil foundation, this research verifies that the SSI effect must be carefully understood before a TMD control system is designed to determine if the control is necessary and if the SSI effect must be considered when choosing the optimal parameters of the TMD device.

Shaking Table Model Test of Isolated Structure on Soft Site and Analysis on Its Isolation Efficiency

Adopting a soft site model built on soft interlayer soil foundation,a shaking table test for soft interlayer soil-isolated structure interaction is conducted to investigate the seismic response of isolated structure on soft site,and analyze its isolation effect.Test results show that the test can reflect the earthquake response characteristics of isolated structure on soft site.It is on soft site that the dynamic characteristics of isolated structure,acceleration magnification factor(AMF)of isolated structure and isolation efficiency of the isolation layer differ from those on rigid foundation with an soil-structure interaction(SSI)effect,represented by the reduction in fundamental vibration frequency of isolated structure and the increase of damping ratio with changes of the SSI effect.SSI can either increase or decrease AMF of isolated structure on soft site,depending on the characteristics of earthquake motion input.Furthermore,the isolation efficiency of isolation layer on soft site is decreased with the SSI effect,which is related to the peak ground acceleration(PGA)and the characteristics of earthquake motion input.

Numerical analysis on seismic performance of underground structures in liquefiable interlayer sites from centrifuge shaking table test

When an underground structure passes through a liquefiable soil layer,the soil liquefaction may pose a significant threat to the structure.A centrifuge shaking table test was performed to research the seismic response of underground structures in liquefiable interlayer sites,and a valid numerical model was obtained through simulation model test.Finally,the calibrated numerical model was used to perform further research on the influence of various distribution characteristics of liquefiable interlayers on the seismic reaction of underground structures.The key findings are as follows.The structure faces the most unfavorable condition once a liquefiable layer is located in the middle of the underground structure.When a liquefiable layer exists in the middle of the structure,the seismic reactions of both the underground structure and model site will increase with the rise of the thickness of the liquefiable interlayer.The inter-story drift of the structure in the non-liquefiable site is much smaller than that in the liquefiable interlayer site.The inter-story drift of the structure is not only associated with the site displacement and the soil-structure stiffness ratio but also closely associated with the slippage of the soil-structure contact interface under the condition of large deformation of the site.

Modeling, identification and compensation for geometric errors of laser annealing table

In order to improve the process precision of an XY laser annealing table, a geometric error modeling, and an identification and compensation method were proposed. Based on multi-body system theory, a geometric error model for the laser annealing table was established. It supports the identification of 7 geometric errors affecting the annealing accuracy. An original identification method was presented to recognize these geometric errors. Positioning errors of 5 lines in the workspace were measured by a laser interferometer, and the 7 geometric errors were identified by the proposed algorithm. Finally, a software-based error compensation method was adopted, and a compensation mechanism was developed in a postprocessor based on LabVIEW. The identified geometric errors can be compensated by converting ideal NC codes to actual NC codes. A validation experiment has been conducted on the laser annealing table, and the results indicate that positioning errors of two validation lines decreased from ±37 μm and ±33 μm to ±5 μm and ±4.5 μm, respectively. The geometric error modeling, identification and compensation method presented in this work can be straightforwardly extended to any configurations of 2-dimensional worktable.

Impact of water table on hierarchically nested groundwater flow system

Water table configuration gives rise to hierarchically nested groundwater flow systems.However,there remains a lack of comprehensive understanding regarding the controlling factors of water table and its impact on flow systems.Moreover,it remains challenging to identify characteristics of water table space variation through limited groundwater observations at the regional scale.Based on two ideal two-dimensional cross-section analytical models,this study presents a simplified approach to preliminarily assess the nonlinear interactions between water table variation and three driving factors:Topography,geol-ogy and climate.Two criteria,C1 and C2,are utilized to address issues at different scales ranging from basin to local:(i)the influence of various factors on water table configuration;and(ii)the influence of water table on groundwater flow pattern.Then,the Ordos Plateau is taken as an example to explore the role of the water table in nested groundwater systems using the provided approach and criterion.The applica-tion of this approach in the Ordos Plateau demonstrates its appropriateness as a practical method for prelim-inarily determining the characteristics of water table configuration and its impact on flow systems.The study explores the mechanism influencing spatial variation in the water table and improves understanding of the interaction between topography,geology,and climate on groundwater flow patterns.

Scaled down model design of shaking table test of Taizhou Bridge

Taizhou Bridge is the first kilometer level three-pylon two-span suspension bridge in the world and the structural complexity has significant effects on the seismic performance of the bridge. Shaking table test of Taizhou Bridge is arranged to investigate the effects of non-uniform ground motion input, collision between main and side spans and optimal seismic structural system. It's very important and difficult to design and manufacture the scaled down model of Taizhou Bridge used during the shaking table test. The key point is that the girder and pylons are very hard to be manufactured if the similarity ratio is strictly followed. Based on the finite element method (FEM) analysis, a simplified scaled down model is designed and the bending stiffness of the girder and pylon are strictly simulated, and the torsion stiffness and axial stiffness are not strictly simulated. The inner forces and displacements of critical sections, points of simplified model and theoretical model are compared by FEM analysis, and it's found out that the difference between the seismic responses is relatively small. So, the simplified model can be used to conduct the shaking table test by the FEM verification.

Growth models and site index table of natural Korean pine forests

According to the growth characteristics of natural Korean pine (Pinus Koraiensis) forests, 6 equations such as Chapman-Richards equation, Logistic equation, Power equation, and so on were selected to ftt for the growth modeIs for Korean pine forest. The growth models were developed based on 208 random trees and 24o dominant trees. Results show that the Chapman-Richards equation is the best model for estimating tree height by age and DBH, while the Parabola equation is fittest for predicting DBH by age or estimating age from DBH. The site index table of Korean pine forest was compiled by using the proportional method with the Chapman-Richards equation as the guide curve and vaIidated by accuracy test.

A Multivariate Test for Three-Factor Interaction in 3-Way Contingency Table under the Multiplicative Model

Two test statistics that have been commonly used in analysing interactions in contingency table are the Pearson’s Chi-square statistic, χ2, and likelihood ratio test statistic, G2. Both test statistics, in tables with sufficiently large sample size, have an asymptotic chi-square distribution with degrees of freedom (df) equal to the number of free parameters in the saturated model. For example under the hypothesis of independence of the row and column conditioned on the layer in an I × J × K contingency table, the df is K(I –1)(J– 1). These test statistics, in large sized tables, will have less power since they have large degrees of freedom. This paper proposes a product effect model, which combines the advantages of the multiplicative models over the additive, for analysing the interaction between the row and column of the 3-way table conditioned on the layer. The derived statistics is shown to be asymptotically chi-square with a small degree of freedom, K?– 1, for the I × J × K contingency table. The performance of the developed statistic is compared with the Pearson’s chi-square statistic and the likelihood ratio statistic test using an illustrative example. The results show that the product effect test can detect interaction even when some of the main effects are not significant and can perform better than the other competitors having smaller degree of freedom in large sized tables.

Numerical Modeling of Shallow Water Table Behavior with Lisse Effect

Air entrapment is an important consideration in environments with shallow water tables and sandy soil, like the condition of highly conductive sandy soils and flat topography in Florida, USA. It causes water table rises in soils, which are significantly faster and higher than those in soils without air entrapment. Two numerical models, Integrated Hydrologic Model (IHM) and HYDRUS-1D (a single-phase, one-dimensional Richards′ equation model) were tested at an area of west central Florida to help further understanding the shallow water table behavior during a long term air entrapment. This investigation employed field data with two modeling approaches to quantify the variation of air pressurization values. It was found that the air pressurization effect was responsible at time up to 40 cm of water table rise being recorded by the observation well for these two models. The values of air pressurization calculated from IHM and HYDRUS-1D match the previously published values. Results also indicated that the two numerical models did not consider air entrapment effect (as the predictive parameters remain uncertain) and thus results of depth to water table from these models did not compare to the observations for these selected periods. Incorporating air entrapment in prediction models is critical to reproduce shallow water table observations.

Stable Routh-Padé-type approximation in model reduction of interval systems

An interval Pade-type approximation is introduced and then Routh-Pade-type method （IRPTM） is presented to model reduction in interval systems. The denominator in reduced model is obtained from the stable Routh table, and its numerator is constructed by the interval Pade-type definition. Compared to the existing Routh-Pade method, IRPTM does not need to solve linear interval equations theoretical analysis shows that IRPTM has example is given to illustrate our method. Hence, we do not have to compute smaller computational cost than that interval division in the process. Moreover, of Routh-Pade method. A typical numerical

JTable组件的深入剖析

JTable组件是一个综合性的Java界面开发组件,内部包含一套独立的消息传递机制,以协调整个组件的运作。文中对JTable组件进行了深入的分析,介绍了JTable组件采用的设计模式、消息的传递方法、JTable的使用、TableModel的常用方法、如何向JTable传递消息及如何实现对JTable的控制。最后,介绍了单元渲染器和编辑器的实现和使用。

Shaking table test and numerical analysis of offshore wind turbine tower systems controlled by TLCD

A wind turbine system equipped with a tuned liquid column damper （TLCD） is comprehensively studied via shaking table tests using a 1/13-scaled model. The effects of wind and wave actions are considered by inputting response- equivalent accelerations on the shaking table. The test results show that the control effect of the TLCD system is significant in reducing the responses under both wind-wave equivalent loads and ground motions, but obviously varies for different inputs, Further, a blade-hub-tower integrated numerical model for the wind turbine system is established. The model is capable of considering the rotational effect of blades by combining Kane＇s equation with the finite element method. The responses of the wind tower equipped with TLCD devices are numerically obtained and compared to the test results, showing that under both controlled and uncontrolled conditions with and without blades＇ rotation, the corresponding responses exhibit good agreement. This demonstrates that the proposed numerical model performs well in capturing the wind-wave coupled response of the offshore wind turbine systems under control. Both numerical and experimental results show that the TLCD system can significantly reduce the structural response and thus improve the safety and serviceability of the offshore wind turbine tower systems. Additional issues that require further study are discussed.

Shake table testing of a multi-tower connected hybrid structure

Many single-tower reinforced concrete core wall-steel frame （RCC-SF） buildings have been built in China, but there are no buildings of different-height multi-tower hybrid system. A multi-tower RCC-SF tall building was thus studied because of its structural complexity and irregularity. First, a 1/15 scaled model structure was designed and tested on the shake table under minor, moderate, and major earthquake levels. Then, the dynamic responses of the model structure were interpreted to those of the prototype structure according to the similitude theory. Experimental results demonstrate that, despite the complexity of the structure, the lateral deformation bends as the ＂bending type＂ and the RC core walls contribute more than the steel frames to resist seismic loads. The maximum inter-story drift of the complex building under minor earthquakes is slightly beyond the elastic limitation specified in the Chinese code, and meets code requirements under major earthquakes. From the test results some suggestions are provided that could contribute favorable effect on the seismic behavior and the displacement of the building.

QFT Robust Control Design for 3-Axis Flight Table Servo System with Large Friction

The 3-axis flight table is an important device and a typical high performanceposition and speed servo system used in the hardware-in-the-loop simulation of flight controlsystem. Friction force and uncertainty are the main characteristics in the 3-axis flight table servosystem. Based on the description of dynamic and static model of a nonlinear Stribeck frictionmodel, and taking account of the practical uncertainties of 3-axis flight table servo system, theQFT controller is designed. Simulation and realtime results are presented.

Advanced run-out table cooling technology based on ultra fast cooling and laminar cooling in hot strip mill

In order to meet the severe requirements of market and reduce production costs of high quality steels,advanced run-out table cooling based on ultra fast cooling(UFC) and laminar cooling(LC) was proposed and applied to industrial production.Cooling mechanism of UFC and LC was introduced first,and then the control system and control models were described.By using UFC and LC,low-cost Q345B strips had been produced in a large scale,and industrial trials of producing low-cost dual phase strips were completed successfully.Application results show that the ultra fast cooling is uniform along the strip width and length,and does not affect the flatness of strips.The run-out table cooling system runs stably with a high precision,and makes it possible for the user to develop more high quality steels with low costs.

Automatic Table Recognition and Extraction from Heterogeneous Documents

This paper examines automatic recognition and extraction of tables from a large collection of het-erogeneous documents. The heterogeneous documents are initially pre-processed and converted to HTML codes, after which an algorithm recognises the table portion of the documents. Hidden Markov Model (HMM) is then applied to the HTML code in order to extract the tables. The model was trained and tested with five hundred and twenty six self-generated tables (three hundred and twenty-one (321) tables for training and two hundred and five (205) tables for testing). Viterbi algorithm was implemented for the testing part. The system was evaluated in terms of accuracy, precision, recall and f-measure. The overall evaluation results show 88.8% accuracy, 96.8% precision, 91.7% recall and 88.8% F-measure revealing that the method is good at solving the problem of table extraction.

Shaking Table Test of Pile-Water-Pier Superstructure

The model test of seismic simulation shaking table is an important method to study the seismic design of bridge structure. In order to evaluate the seismic response and dynamic characteristics of pile-water-pier system for developing more reliable design procedures, shaking table model tests of a submerged bridge pier system, including pile groups-cap-pier and inertia mass, were conducted. Since different similitude laws corresponding to different test objectives affected the validity of test results, the similitude law with the aim to consider the effect of hydrodynamic pressure was proposed and confirmed through an actual example. Based on the test results, the effect of water around model on seismic response under seismic excitation input was analyzed and the failure level was judged by observing the variation of basic frequency. The test results indicate that the transfer function of analytical model with water is different from that without water, the natural frequency without water is always higher than that with water, and the first modal shapes are various. It is also concluded that the similitude law is suitable for practical application and the dynamic characteristics and seismic response of the structure system can be changed because of the existence of the surrounding water, which should be paid much attention in the further investigation.

Dynamics and Control of Grinding Machine with Micropositioning Workpiece Table

To improve the machining precision of a surface grinding machine, a micropositioning workpiece table with high performance was used as auxiliary infeed mechanism to implement nanometer level positioning and dynamic compensation. To better understand the characteristics of the grinding machine modulated with micropositioning workpiece table, the dynamic model of the grinding system was established with modal synthesis and Lagrange＇s equation methods. The grinding system was divided into five subsystems. For each subsystem, the generalized kinematic and potential energies were obtained. Accordingly the dynamic model of the grinding system was given in the modal domain. The waviness of the grinding process was achieved based on the wheel and workpiece vibration. A nonlinear proportional integral derivative （PID） controller with differential trackers was developed to realize dynamic control. The simulation results show that the machining accuracy of the workpiece can be effectively improved by utilizing the micropositioning workpiece table to implement dynamic compensation. An experimental test was carried out to verify the proposed method, and the waviness of the workpiece can be reduced from 0.46 μm to 0.10 μm.

Deformation and localisation behaviours of reinforced gravelly backfill using shaking table tests

To understand the deformational behaviours of geosynthetics-reinforced soil retaining walls(GRS RWs),a series of plane-strain shaking table tests was conducted on retaining wall models.The backfill of the models was made of poorly graded gravel.Deformations and strains in the gravelly backfill induced by seismic loading are recorded in real time,which are of importance to understand the seismic strength and stability of the GRS RW systems,as strain localisation development in the backfill and foundation is related to the degree of strength degradation of the system.In the present study,we aimed at quantifying the induced deformations of the GRS RW models due to shaking.Digital image correlation(DIC)technique was then employed to analyse and provide full-field deformation and motion images with the models.It is demonstrated that,unlike conventional contact devices that are yet limited to provide quantities of a singular and fixed location,DIC provides deformation and motion of the area of interests to reveal the evolution of localisation.